Obertíada

Sunday, April 26, 2009

THE PLEIADES ON APRIL 26, 2009

THE PLEIADES____________

Known pre-historically. Mentioned by Homer about 750 B.C., by biblical Amos about 750 B.C., and by Hesiod about 700 B.C.

The Pleiades, also known as Messier 45 (M45), are among those objects which are known since the earliest times. At least 6 member stars are visible to the naked eye, while under moderate conditions this number increases to 9, and under clear dark skies jumps up to more than a dozen (Vehrenberg, in his Atlas of Deep Sky Splendors, mentions that in 1579, well before the invention of the telescope, astronomer Moestlin has correctly drawn 11 Pleiades stars, while Kepler quotes observations of up to 14).

Modern observing methods have revealed that at least about 500 mostly faint stars belong to the Pleiades star cluster, spread over a 2 degree (four times the diameter of the Moon) field. Their density is pretty low, compared to other open clusters. This is one reason why the life expectation of the Pleiades cluster is also pretty low (see below).

According to Kenneth Glyn Jones, the earliest known references to this cluster are mentionings by Homer in his Ilias (about 750 B.C.) and his Odyssey (about 720 B.C.), and by Hesiod, about 700 B.C.. According to Burnham, they were seen in connection to the agricultural seasons of that time. Also, and the Bible has three references to the Pleiades (the Hebrew "Kiymah"): Job 9:7-9, Job 38:31-33, and Amos 5:8; the prophet Amos is believed to have given his message in 750 B.C. or 749 B.C., while there is no consent on the dating of the book of Job: Some believe it was written about 1,000 B.C. (the regency of Kings David and Solomon in old Israel) or earlier (Moses, about 13th to 16th century B.C.), others give reasons that it may have been created as late as the 3rd to 5th century B.C.. The present author [hf] does not know if the cluster is mentioned in one of the earlier Assyrian or Sumerian sources.

The Pleiades also carry the name "Seven Sisters"; according to Greek mythology, seven daughters and their parents. Their Japanese name is "Subaru", which was taken to christen the car of same name. The Persian name is "Soraya", after which the former Iranian empress was named. Old European (e.g., English and German) names indicate they were once compared to a "Hen with Chicks". Other cultures tell more and other lore of this naked-eye star cluster. Ancient Greek astronomers Eudoxus of Knidos (c. 403-350 BC) and Aratos of Phainomena (c. 270 BC) listed them as an own constellation: The Clusterers. This is also referred to by Admiral Smyth in his Bedford Catalog.

Burnham points out that the name "Pleiades" may be derived from either the Greek word for "to sail", or the word "pleios" meaning "full" or "many". The present author prefers the view that the name may be derived from the mythological mother, Pleione, which is also the name of one of the brighter stars.

According to Greek mythology, the main, visible stars are named for the seven daughters of "father" Atlas and "mother" Pleione: Alcyone, Asterope (a double star, also sometimes called Sterope), Electra, Maia, Merope, Taygeta and Celaeno. Bill Arnett has created a map of the Pleiades with the main star names. These stars are also labeled in a labeled copy of the UKS image which appears in this page.

__________________________________

Also note the Pleiades map. Today, April 26, 2009 at sunset, they can be seen with the naked eye, to the West, midway between the Moon and Mercury.__________________________________

In 1767, Reverend John Michell used the Pleiades to calculate the probability to find such a group of stars in any place in the sky by chance alignment, and found the chance to be about 1/496,000. Therefore, and because there are more similar clusters, he concluded correctly that clusters should be physical groups (Michell 1767).

On March 4, 1769, Charles Messier included the Pleiades as No. 45 in his first list of nebulae and star clusters, published 1771.

About 1846, German astronomer Mädler (1794-1874), working at Dorpat, noticed that the stars of the Pleiades had no measurable proper motion relative to each other; from this he boldly concluded that they form a motionless center of a larger stellar system, with star Alcyone in the center. This conclusion was to be, and was, rejected by other astronomers, in particular Friedrich Georg Wilhelm Struve (1793-1864). Nevertheless, the common proper motion of the Pleiades was a proof that they move as a group in space, and a further hint that they form a physical cluster.

Longer exposure photographs (and also short focal ratio, i.e. short focal length compared to their aperture, "rich field" telescopes of considerably good quality, especially good binoculars) have revealed that the Pleiades are apparently imbedded in nebulous material, obvious in one of the images, which was taken by David Malin with the UK Schmidt Telescope, and is copyrighted by the Royal Observatory Edinburgh and the Anglo-Australian Observatory.

The Pleiades nebulae are blue-colored, which indicates that they are reflection nebulae, reflecting the light of the bright stars situated near (or within) them.

The brightest of these nebulae, that around Merope, was discovered on October 19, 1859 by Ernst Wilhelm Leberecht (Wilhelm) Tempel at Venice (Italy) with a 4-inch refractor; it is included in the NGC as NGC 1435. Leos Ondra has made the biography of Wilhelm Tempel available online together with a drawing of the Merope Nebula, and has agreed to include it in this database.

The extension to Maia was discovered by the brothers Paul and Prosper Henry in Paris on a photographic plate taken on November 16, 1885; this is NGC 1432 or the Maia Nebula.

The nebulae around Alcyone, Electra, Celaeno and Taygeta were found on photographs in the later 1880s.

The full complexity of the Pleiades nebulae was revealed by the first astro cameras, e.g. by that of the brothers Henry in Paris and Isaac Roberts in England, between 1885 and 1888.

In 1890, E.E. Barnard discovered a starlike concentration of nebulous matter very close to Merope, which found its way into the IC as IC 349.

The analysis of the spectra of the Pleiades nebulae by Vesto M. Slipher in 1912 reveiled their nature as reflection nebulae, as their spectra are exact copies of the spectra of the stars illuminating them.

Physically, the reflection nebula is probably part of the dust in a molecular cloud, unrelated to the Pleiades cluster, which happens to cross the cluster's way. It is not a remainder of the nebula from which the cluster once formed, as can be seen from the fact that the nebula and cluster have different radial velocities, crossing each other with a relative velocity of 6.8 mps, or 11 km/sec.

According to new calculations published by a team from Geneva (Meynet et.al. 1993), the age of the Pleiades star cluster amounts 100 million years. This is considerably more than the previously published "canonical" age of 60--80 million years (e.g., the Sky Catalog 2000's 78 million).

It has been calculated that the Pleiades have an expected future lifetime as a cluster of only about another 250 million years (Kenneth Glyn Jones); after that time, they will have been spread as individual (or multiple) stars along their orbital path.

The distance of the Pleiades cluster has been newly determined by direct parallax measures by ESA's astrometric satellite Hipparcos; according to these measurement, the Pleiades are at a distance of 380 light years (previously, a value of 408 light years had been assumed). This value would have required an explanation for the comparatively faint apparent magnitudes of the Pleiades stars.

However, subsequent investigations with the Hubble Space Telescope and the Mount Palomar and Mount Wilson Observatories have finally shown that the Hipparcos distance is probably too small: By acurate parallaxes of Pleiades stars, this cluster is at a distance of 440 +/-6 light-years.

The Trumpler classification is given for the Pleiades as II,3,r (Trumpler, according to Kenneth Glyn Jones) or I,3,r,n (Götz and Sky Catalog 2000), meaning that this cluster appears detached and strong or moderately concentrated toward its center, its stars are spread in a large range of brightness, and it is rich (has more than 100 members).

Some of the Pleiades stars are rapidly rotating, at velocities of 150 to 300 km/sec at their surfaces, which is common among main sequence stars of a certain spectral type (A-B). Due to this rotation, they must be (oblate) spheroids rather than spherical bodies. The rotation can be detected because it leads to broadened and diffuse spectral absorption lines, as parts of the stellar surface approach us on the one side, while those on the opposite side recede from us, relative to the star's mean radial velocity.

The most prominent example for a rapidly rotating star in this cluster is Pleione, which is also variable in brightness between mag 4.77 and 5.50 (Kenneth Glyn Jones).

It was spectroscopically observed that between the years 1938 and 1952, Pleione has ejected a gas shell because of this rotation, as had been predicted by O. Struve.

These dwarf stars give rise to a specific problem of stellar evolution: How can white dwarfs exist in such a young star cluster ?

As it is not only one, it is most certain that these stars are original cluster members and not all field stars which have been captured (a procedure which does not work effectively in the rather loose open clusters anyway).

From the theory of stellar evolution, it follows that white dwarfs cannot have masses above a limit of about 1.4 solar masses (the Chandrasekhar limit), as they would collapse due to their own gravitation if they were more massive. But stars with such a low mass evolve so slow that it takes them billions of years to evolve into that final state, not only the 100 million year age of the Pleiades cluster.

The only possible explanation seems to be that these WD stars were once massive so that they evolved fast, but due to some reason (such as strong stellar winds, mass loss to close neighbors, or fast rotation) have lost the greastest part of their mass. Possibly they have, in consequence, lost another considerable percentage of their mass in a planetary nebula. Anyway, the final remaining stars (which was previously the star's core) must have come below the Chandrasekhar limit, so that they could go into the stable white dwarf end state, in which they are now observed.

New observations of the Pleiades since 1995 have revealed several candidates of an exotic type of stars, or starlike bodies, the so-called Brown Dwarfs.

These hitherto hypothetical objects are thought to have a mass intermediate between that of giant planets (like Jupiter) and small stars (the theory of stellar structure indicates that the smallest stars, i.e. bodies that produce energy by fusion somewhen in their lifetime, must have at least about 6..7 percent of one solar mass, i.e. 60 to 70 Jupiter masses).

So brown dwarfs should have 10 to about 60 times the mass of Jupiter. They are assumed to be visible in the infrared light, have a diameter of about or less that of Jupiter (143,000 km), and a density 10 to 100 times that of Jupiter, as their much stronger gravity presses them tougher together.

Apparently surrounding Aldebaran is another, equally famous open cluster, the Hyades; Aldebaran is known to be a non-member foreground star (at 68 light years distance, compared to 150 ly for the Hyades).

The cluster is a great object in binoculars and rich-field telescopes, showing more than 100 stars in a field about 1 1/5 degrees in diameter. In telescopes, it is frequently even too large to be seen in one lowest magnification field of view. A number of double and multiple stars are contained in the cluster.

The Merope Nebula NGC 1435 requires a dark sky and is best visible in a rich-field telescope (Tempel had discovered it with a 4-inch telescope).

As the Pleiades are situated close to the ecliptic (4 degrees off), occultations of the cluster by the Moon occur quite frequently: This is a very appealing spectacle, especially for amateurs with less expensive equipment (actually, you can observe it with the naked eye, but even the smallest binoculars or telescopes will increase observing pleasure -- the March 1972 Pleiad occultation was one of the first amateur astronomical experiences of the present author).

Such events demonstrate the relations of the apparent sizes of the Moon and the cluster: Burnham points out that the Moon may be "inserted into the quadrangle formed by" Alcyone, Electra, Merope and Taygeta (Maia, and possibly Asterope, is occulted in this situation).

Also, planets come close to the Pleiades cluster (Venus, Mars, and Mercury even occasionally pass through) to give a conspicuous spectacle.

As mentioned in the description for the Orion Nebula M42, it is a bit unusual that Messier added the Pleiades (together with the Orion Nebula M42/M43 and the Praesepe cluster M44) to his catalog, and will perhaps stay subject to speculation.

He was not a mathematician but trained in medicine and made his original contributions to the subject.

However, as the leading translator in the HOUSE OF WISDOM at one of the most remarkable periods of mathematical revival, his influence on the mathematicians of the time is of sufficient importance to merit his inclusion in this archive.

His son Ishaq ibn Hunayn, strongly influenced by his father, is famed for his Arabic translation of Euclid's Elements.

Hunayn's father was Ishaq, a pharmacist from Hira. The family were from a group who had belonged to the Syrian Nestorian Christian Church before the rise of Islam, and Hunayn was brought up as a Christian.

Hunayn became skilled in languages as a young man, in particular learning Arabic at Basra and also learning Syriac.

To continue his education Hunayn went to Baghdad to study medicine under the leading teacher of the time.

However, after falling out with this teacher, Hunayn left Baghdad and, probably during a period in Alexandria, became an expert in the Greek language.

Hunayn returned to Baghdad and established contact with the teacher with whom he had fallen out. The two became firm friends and were close collaborators on medical topics for many years.

Let us go back to a time before Hunayn was born and describe the events which would lead to a remarkeble period of scholarship.

Harun al-Rashid became the fifth Caliph of the Abbasid dynasty on 14 September 786.

He brought culture to his court and tried to establish the intellectual disciplines which at that time were not flourishing in the Arabic world. It was during al-Rashid's reign that the first Arabic translation of Euclid's Elements was made by al-Hajjaj. The first steps began to be taken which would allow Greek knowledge to spread through the Islamic empire, a process in which Hunayn was to play a major role.

Al-Rashid had two sons, the eldest was al-Amin while the younger was al-Ma'mun. Harun al-Rashid died in 809, the year after Hunayn's birth, and there was an armed conflict between his two sons. Al-Ma'mun won the armed struggle, became Caliph and ruled the empire from Baghdad. He continued the patronage of learning started by his father and founded an academy called the House of Wisdom where Greek philosophical and scientific works were translated.

It should not be thought that the Arabs who were translating these Greek texts simply sat down with a pile of Greek manuscripts and translated them. Most of the difficulty occurred in searching for the manuscripts which were to be translated. In order to find manuscripts of the works of Aristotle and others, al-Ma'mun sent a team of his most learned men to Byzantium. It is thought that Hunayn, being more skilled in the Greek language than any of the other scholars in Baghdad, was on this expedition.

As an example of the lengths that Hunayn went in order to find a particular manuscript we quote his description of a search for a medical manuscript (see for example):

"I sought for [the manuscript] earnestly and travelled in search of it in the lands of Mesopotamia, Syria, Palestine and Egypt, until I reached Alexandria, but I was not able to find anything, except about half of it at Damascus."

Al-Ma'mun recruited the most talented men for the House of Wisdom such as al-Khwarizmi, al-Kindi and al-Hajjaj the first translator of Euclid's Elements into Arabic refered to above. There they worked with Hunayn and later also with Thabit ibn Qurra.

Hunayn became a close friend of Muhammad Banu Musa although relations between some of the scholars was not good due to rivalry.

In 833 al-Ma'mun died and was succeeded by his brother al-Mu'tasim. The house of Wisdom continued to flourish under successive caliphs. Al-Mu'tasim died in 842 and was succeeded by al-Wathiq.

Hunayn soon became famous and participated in the scholarly meetings at which physicians and philosophers discussed dificult problems in the presence of Caliph al-Wathiq.

Caliph al-Wathiq was succeeded as Caliph in 847 by al-Mutawakkil who appointed Hunayn to the post of chief physician at his court, a position he held for the rest of his life.

Under both these Caliphs internal arguments and rivalry arose between the scholars in the House of Wisdom and Hunayn was most certainly involved in this rivalry. The rivalry could certainly become serious and at one point Hunayn had his library confiscated and he was imprisoned.

Hunayn is important for the many excellent translations of Greek texts which he made into Arabic.

In particular he translated Plato and Aristotle. These translations were spread widely through Mesopotamia, Syria and Egypt.

Wednesday, April 15, 2009

CATALONIA

Autonomous region (pop.9.165,638), NE Spain, stretching from the Pyrenees at the French border southward along the Mediterranean Sea.

LAND and ECONOMY

Catalonia comprises four provinces, named after their capitals: Barcelona, Girona, Lleida, and Tarragona.

Barcelona, the historic capital, contains more than a third of the region's residents. Catalan and Spanish have been the official languages of Catalonia since 1978, which has led to a considerable revival of Catalan.

Mostly hilly, with pine-covered mountains, it also has some highly fertile plains. Cereals, olives, and grapes are grown, and one third of the wines of Spain are produced there.

The Ebro (Ebre, in Catalan), Segre, and Cinca rivers furnish hydroelectric power for the industries in Barcelona and Girona provs.; chief products are textiles, chemicals, automobiles, airplanes, locomotives, and foundry and other metal items. The service sector has grown rapidly.

HISTORY

Trade has been active along the coast since Greek and Roman times. The history of medieval Catalonia is that of the Counts of Barcelona. They emerged in the nineteenh century (9th cent) as the chief lords in the Hispanic Mark founded by Charlemagne.

In 1137,through marriage(see Raymond Berengar IV), Catalonia united with Aragon in a Catalan-Aragonese Confederation. Ramon Berenguer IV married Petronela of Aragon and became King of Aragon.Nevertheless Catalonia preserved its own Laws, Courts and language. And so did Aragon.

ART AND CULTURE

Catalan art and Catalan literature flourished in the Middle Ages.

In the cities, notably Barcelona, the burgher and merchant classes grew very powerful.

Catalan traders rivaled those of Genoa and Venice, and their maritime code was widely used in the 14th cent.

They, and adventurers like Roger de Flor, were largely responsible for the expansion in the Mediterranean of the house of Aragón (see Aragón, house of).

Catalonia failed in its rebellion (1461–72) against John II, and after the union with Castile, and the first bubonic plague, Catalonia declined.

The centralizing policy of the Spanish kings, the shifting of trade routes with the consequent loss of commercial income, pirate attacks, and recurring plagues and famines were all major factors.

Agitation for autonomy was always strong.

In the Thirty Years War (1618–48), Catalonia rose against Philip IV and in the War of the Spanish Succession it sided with Archduke Charles of Austria against Philip V of France. Who in reprisal deprived Catalonia of its own Governmental Organs.

In the late 19th and early 20th cent. it was a center of socialist and anarchist strength. In 1931 the Catalans established a separate government, first under Francesc Macià, then under Lluis Companys, which in 1932 won autonomy from the Spanish Cortes.

A revolution (1934) for complete independence failed, but in 1936 autonomy was restored. In the civil war of 1936–39, Loyalist Catalonia sided with the Republic and suffered heavily for its opposition to Franco. Barcelona was the Loyalist capital from Oct., 1936 to Jan., 1939. Catalonia fell to Franco in Jan 26 1939.

Under the Franco dictatorship, the use of Catalan was banned in public life.

After Franco´s death democracy was restored and then couldCatalonia elect its first Parliament as an Atonomous region in 1980.And by the mid-1990s Catalan nationalists had become a force in both Catalonian and Spanish politics.

Increased autonomy for Catalonia and recognition of the region as a "nation" within Spain was approved in 2006.

Sunday, April 12, 2009

DON'T MISS BEAUTY - STOP AND LISTEN

JOSHUA BELL___________

A man sat at a metro station in Washington DC and started to play the violin; it was a cold January morning. He played six Bach pieces for about 45 minutes. During that time, since it was rush hour, it was calculated that thousand of people went through the station, most of them on their way to work.

Three minutes went by and a middle aged man noticed there was musician playing. He slowed his pace and stopped for a few seconds and then hurried up to meet his schedule..

A minute later, the violinist received his first dollar tip: a woman threw the money in the till and without stopping continued to walk.

A few minutes later, someone leaned against the wall to listen to him, but the man looked at his watch and started to walk again. Clearly he was late for work.

The one who paid the most attention was a 3 year old boy. His mother tagged him along, hurried but the kid stopped to look at the violinist. Finally the mother pushed hard and the child continued to walk turning his head all the time. This action was repeated by several other children. All the parents, without exception, forced them to move on.

In the 45 minutes the musician played, only 6 people stopped and stayed for a while. About 20 gave him money but continued to walk their normal pace. He collected $32. When he finished playing and silence took over, no one noticed it. No one applauded, nor was there any recognition.

No one knew this but the violinist was Joshua Bell, one of the best musicians in the world. He played one of the most intricate pieces ever written with a violin worth 3.5 million dollars.

Two days before his playing in the subway, Joshua Bell sold out at a theater in Boston and the seats average $100.

This is a real story. Joshua Bell playing incognito in the metro station was organized by the Washington Post as part of a social experiment about perception, taste and priorities of people.

The outlines were:

In a commonplace environment at an inappropriate hour: Do we perceive beauty? Do we stop to appreciate it? Do we recognize the talent in an unexpected context?

One of the possible conclusions from this experience could be:

If we do not have a moment to stop and listen to one of the best musicians in the world playing the best music ever written, how many other things are we missing?

These QUOTES seem to all refer to the same annoying substances, but they don't. In fact, the substances they refer to aren't even from the same planet.

The first two quotes are from Alaska, where people are dealing with volcanic ash from the ongoing eruption of Mount Redoubt.

The next two come from the Moon, where Apollo astronauts once dealt with a similar problem: moondust.

FOTO : Mt. Redoubt has erupted at least 19 times since March 22, 2009. Alaska photographer Thomas Kerns took this picture of the volcano in action on March 31st.

"Volcanic ash and moondust have a lot in common," says Carole McLemore of the Marshall Space Flight Center. "Both coat things and stick to them, are grimy, abrasive, damaging to equipment and vehicles, susceptible to electric charging, and risky to inhale.

"Mount Redoubt is giving Alaskans a taste of life on the Moon!"

The stories Alaskans and astronauts tell reveal some of the parallels:

Charles Sloan, a retired hydrogeologist living in Anchorage, has experienced ash first hand. He was around for one of Mount Redoubt's previous eruptions in 1989 and remembers a particularly harrowing incident.

An international carrier flight -- a large jet -- flew into the hot ash plume from the volcano. The ash was sucked into the engines, causing them to shut down, and the plane plummeted!" All 245 terrified passengers on board KLM flight 867 held their breaths. The plane dropped more than 2 miles before the crew could get the engines restarted! It limped in to an emergency landing in Anchorage."

"That was the third such incident over a five year period," adds Tom Miller, former director and now scientist emeritus of the Alaska Volcano Observatory** in Anchorage.

Way back in 1972, astronauts Gene Cernan and Jack Schmitt experienced their own transportation problems when their moonbuggy lost a fender. That doesn't sound like a disaster on the scale of a plummeting airplane,... but when moondust is involved, even a lost fender can have serious consequences.

FOTO: Dust flies from the tires of a moonbuggy driven by Apollo 17 astronaut Gene Cernan. When a fender fell off, plumes of high-flying dust caused serious problems, which the astronauts solved using duct tape: full story.

A rolling moonbuggy without a fender kicks up a "rooster tail" of moondust, spraying the rover and its occupants with dark, abrasive grit. White spacesuits blackened by dust turn into absorbers of the fierce lunar sun with astronauts overheating dangerously inside. Sharp-edged dust wiped off visors scratch the glass, making helmets difficult to see out of. Watch out for that crater! And moondust has an uncanny way of working itself into hinges, latches and joints, rendering them useless.

The resourceful astronauts repaired the fender with duct tape, but even with all four fenders, Cernan had to dust off the rover at each stop. Getting rid of moondust remained a top priority.

Back in Alaska, Miller relates what happened when Mt. Redoubt erupted just last week: "We lost three seismic stations. The one nearest the volcano was fried – probably due to lightning. When you have a tremendous and powerful explosion of ash, the violent movement of all the ash particles generates static electricity and therefore lightning."

FOTO: Lightning flashes in a roiling cloud of ash over Mt. Redoubt on March 27th. Particles of ash rubbing together in the cloud (like socks rubbing against carpet) are partly responsible for the buildup of electrostatic charge. Photo credit and copyright: Bretwood Higman, Ground Truth Trekking.

Dust particles on the Moon are also electrified, at least in part, by the buffeting of the solar wind.

Earth is protected from the solar wind by our planet's magnetic field, but the Moon has no global magnetic field to ward off charged particles from the sun. Free electrons in the solar wind interact with grains of moondust and, in effect, "charge them up." The electrostatic charges cause moondust to cling tenaciously to everything.

Including your lungs…

Apollo 17 astronaut Gene Cernan suffered from the first recorded case of extraterrestrial hay fever. He was taking off his spacesuit after a moonwalk and the air was filling up with dust knocked off the surface of the suit. "It came on pretty fast," he radioed Houston with a stuffy-nose twang. "I had a significant reaction to the dust," he later recalled. "My turbinates (cartilage plates in the walls of the nasal chambers) became swollen."

Some researchers believe sustained breathing of moondust could be dangerous. The sharp-edged grains are able to make tiny cuts in flesh, and they could easily become stuck in lung tissue. Ash presents a similar hazard.

"With volcanic ash, people are advised to wear particle masks or stay indoors," notes Miller." "It's not poisonous, but people with asthma or emphysema can have problems if they inhale it." "And people who wear contacts have to take their contacts out."

FOTO: An Alaskan moonscape. "Highlights of gray volcanic ash around the snow remind me of craters on the Moon," says photographer Michelle Cosper of Girdwood, Alaska.

Alaska resident Michelle Cosper is one of the people suffering:"My throat is sore and stingy, and it smells vaguely like sulfur outside," she reports from the town of Girdwood, which has received a coating of ash from Redoubt's recent eruptions. "We aren't supposed to walk our dogs or go outside for any other reason unnecessarily. Even local newscasters are wearing face masks."

Moondust and volcanic ash cause many of the same troubles. But that does not mean they are the same thing. Volcanic ash comes from active volcanoes, something the Moon does not have. Liquid rock decompresses and explodes from the volcano's mouth, producing a mixture of 'foamed' glass and micro- and mini-crystals.

Moondust, on the other hand, is created by meteoroids. Space rocks hit the Moon's surface at hundreds of thousands of miles per hour, fusing topsoil into glass and shattering the same into tiny sharp-edged pieces.

NASA is returning to the Moon in ~2020.

Thanks to Mt. Redoubt, Alaskans are already getting a taste of the new frontier.